Page 405 - ILAE_Lectures_2015

Chapter 41

Epilepsy and learning disability

MICHAEL KERR

Institute of Psychological Medicine and Clinical Neurosciences, University of Cardiff

Definition

Learning disability is defined as a composite of:
1. Deficiency in learning (Intelligence Quotient (IQ) less than 70)
2. Difficulties with daily living skills
3. An onset within the developmental period (less than 18 years of age).

Epidemiology

Epidemiological issues in ‘special groups’ are dependent on both the source and age of the
population. Cohort effects, due to year of birth, are important in defining prevalence in both
learning disability1 and epilepsy2. Table 137 shows epidemiological surveys of the prevalence
of epilepsy in people with mental and physical handicap. A survey in an institution for people
with learning disability gave a prevalence of epilepsy of 32%5, while a large community-
based questionnaire survey of health needs in people with a learning disability gives a
prevalence of 22.1%, making epilepsy second only to psychological illness as a comorbidity7.
This can be compared with an estimated prevalence of epilepsy in the general population of
between 0.4 and 1%8.

Table 1. Epidemiological surveys of the prevalence of epilepsy in people with mental and
physical handicap3-7.

Study Sample Prevalence

Corbett et al Children under age 14
(1975)3
Community

SMR 20%

Richardson et al Children up to 22 yrs
(1981)4 Community

MMR 24%

SMR 44%

Mariani et al Institution 32%
(1993)5

Steffenburg et al Children 613 year old
(1995)6 Community

MMR 14%

SMR 24%

Welsh Office Adults
(1995)7
Community-based 22.1%

All MR

MMR: mild mental retardation, IQ 5070; SMR: severe mental retardation, IQ <50